Neisseria gonorrhoeae infects several million Americans annually, leading to excessive morbidity, sterility and occasionally death. The hundreds of millions of dollars spent to detect, treat and prevent gonococcal infection will surely increase as antibiotic resistance increases. Although we better understand the molecular genetic mechanisms involved in regulation of several gonococcal surface structures, little is known about their role in pathogenesis. The objective of this proposal is to investigate the molecular and cellular mechanisms involved in the role of outer membrane protein PII in gonococcal interactions with human neutrophils (PMN) and columnar epithelial cells - cells relevant to gonococcal infection and disease. The specific aims are to: 1) Determine the portion(s) of PII responsible for its biological interactions with PMN and epithelial cells, by identifying proteolytically or chemically derived PII peptides that bind to or block binding of gonococci to host cells. Portions of such peptide(s) will be sequenced and the smallest biologically active fraction(s) synthesized. Affinity-purified antisera and monoclonal antibodies will be used as probes; 2) Characterize and identify PMN and epithelial cell PII receptor(s). Cross-linking reagents, chemical or enzymatic modification of cell surface components, detergent solubilization, monoclonal antibodies, affinity-purified antisera, purified PII, and liposomes will be used; 3) Identify the modulatory effects of purified PII on PMN functions including viability, membrane polarization, calcium fluxes, degranulation, oxidative metabolism, chemotaxis and phagocytosis, and; 4) Study the role of PII in the entrance of gonococci into primary human cervical and endometrial epithelial cells, and continuous human epithelial cell lines.